Secretary of State Hillary Clinton took responsibility Monday night for any security failures leading up to the consulate attack last month in Libya that killed the American ambassador, but she seemed to push back against claims of a cover-up, blaming the "fog of war" for the Obama administration's shifting explanations for the attack.

Ambassador Chris Stevens and three other Americans died in the assault on the consulate in Benghazi. Administration officials initially suggested that the attack was "spontaneous" violence that grew out of protests over an anti-Islam film, rather than a premeditated attack.

It later became clear that intelligence officials suspected terrorism almost immediately, and investigators now think extremists tied to Al Qaeda carried out a coordinated attack, with no evidence that the attack was preceded by a protest outside the consulate.

Clinton, however, attributed the administration's shifting story to "the confusion you get in any type of combat situation."

"Remember, this was an attack that went on for hours," Clinton said in an interview with Fox News during a trip to Peru. "There had to be a lot of sorting out. ... Everyone said, here's what we know, subject to change."

The Obama administration, in particular the State Department, also has faced intense scrutiny on Capitol Hill over the level of security at the consulate, with allegations that requests for increased protection were denied or ignored.

That question was a prominent topic during the vice presidential debate Thursday, when Vice President Biden denied getting any requests for increased security. The White House later clarified that Biden was speaking for himself and the president, not for the State Department.

Clinton seemed Monday to back up Biden's claims, saying decisions about diplomatic security are made by her department.

"I'm responsible for the State Department, for the more than 60,000 people around the world," she said. "The decisions about security are made by security professionals. But we're going to review everything to be sure we're doing what needs to be done in an increasingly risky environment."

She also addressed the question of a June explosion at the consulate in Benghazi that some have argued should have raised a red flag about security.

"I can't speak to who knew what," she said. "We knew there were security breaches and problems throughout Libya. That's something that came about as the aftermath of the revolution to topple Qaddafi, with so many militias formed, so many weapons loose. ... It was taken into account by security professionals as they made their assessments."

Three Republican senators said Clinton's claim was "a laudable gesture," but they put the responsibility for the Benghazi attack and what they called "an escalating pattern of attacks this year in Benghazi" squarely on President Obama and his national security team.

"If the president was truly not aware of this rising threat level in Benghazi, then we have lost confidence in his national security team, whose responsibility it is to keep the president informed. But if the president was aware of these earlier attacks in Benghazi prior to the events of Sept. 11, 2012, then he bears full responsibility for any security failures that occurred," Sens. John McCain of Arizona, Lindsey Graham of South Carolina and Kelly Ayotte of New Hampshire said in a statement released late Monday.

Fox News' Wendell Goler and The Associated Press contributed to this report.